I myself was not my whole family's fuckdoll. As you put it. But I was in my mind so very blessed to have Big sister that's 4 year's older than me. And it still goes on to this day. Has never stopped over the year's it slowed down but never stopped. Our last time was about 5 maybe 6 months ago. So now for roughly 38 years. And I so very much am thankful and love her even more for it.
I am going to say the girl that starts out rubbing the girl riding him is his Girlfriend and the Rider was the older Brother of his rider. And I might be wrong. But In my head that playing out and being there would be a massive Sexual Rush!!! That I would be %100 Down For. But more so I would want it to be my wife as the Rider and her Brother who's only like 11 months younger then her. And I sure would be rooting them on